1. Field of the Invention
The present invention relates to a halogen-free flameproof mesh sheet suitable for being used outdoors such as in a construction work site or engineering work site for a long time.
2. Description of Related Art
A tendency toward an increase in the number of buildings having a large number of stories has been seen recently in the construction industry. Meanwhile, there is also an increase in the number of houses having a small number of stories. It is generally obligatory to lay flameproof mesh sheets in the construction of houses having a small number of stories, as well as scattering prevention flameproof mesh sheets may also be required in these buildings for safety. Regulations regarding such flameproofing are becoming more and more strict.
Currently used flameproof mesh sheets and scattering prevention flameproof mesh sheets can be produced for example, by weaving gray yarn prepared by coating polyester, nylon or polypropylene multi-filament fibers with a vinyl chloride-based paste resin composition and heating. The obtained gray cloth is then subjected to further heating. Alternatively, such yarn can be prepared by coating gray cloth prepared by weaving multi-filament fibers with a vinyl chloride-based paste resin composition and heating, and processing the obtained gray cloth to a desired shape.
The resin composition for coating fibers and cloth comprises for example, a chlorine-containing vinyl chloride resin as the resin and a chlorine-based flame retardant such as chlorinated paraffin, a bromide-based flame retardant such as decabromodiphenyl oxide, or an inorganic flame retardant such as antimony trioxide as a flame retardant (see, for example, Examined Japanese Patent Publication Nos. 52-41786, 53-18065 and 61-9430, as well as Plastics, February, 1991 which are all incorporated herein by reference in their entireties).
In recent years, it has been globally demanded to avoid the use of resins and flame retardants containing elemental halogen which generates harmful gas at the time of combustion from the viewpoint of environmental preservation.
Japanese Laid-Open Patent Publication No. 61-223045 proposes kneading red phosphorus and ammonium phosphate into a polyolefin to prevent corrosion by halogen contained in a halogen-containing compound flame retardant. However, a flame retardant prepared by dispersing ammonium polyphosphate or a metal hydroxide into an aqueous dispersion of an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-vinyl versatate copolymer or an ethylene-vinyl acetate-acrylic ester copolymer, or a dispersion consisting of the above dispersion and a polyurethane aqueous dispersion is not known.
The inventors of the present invention previously proposed a halogen-free flame retardant comprising an aqueous dispersion of a polyolefin resin in Japanese Patent Application No. 9-225464 (incorporated herein by reference in its entirety). Although this flame retardant provides an excellent effect, it has a tendency to increase in viscosity during storage over time.
The present inventors also previously proposed a halogen-free flame retardant containing an aqueous dispersion of an ethylene-vinyl acetate copolymer of 10 to 95 parts by weight of vinyl acetate and the balance consisting of ethylene in Japanese Patent Application No. 9-312550 (incorporated herein by reference in Its entirety). Although this flame retardant provides excellent function and effect, a product thereof has a red tint because red phosphorus is used and it is difficult to color it opaque white or a light vivid color, even by adding titanium oxide or the like. The present invention improves the color and flame retardancy of the flame retardant of JP 9-312550. An opaque white or light vivid color flameproof mesh sheet has been desired in the application field of flameproof mesh sheets.
It is an object of the present invention, which has been made in view of the above situation, to provide a flame retardant for halogen-free flameproof mesh sheets which does not substantially experience an increase in viscosity during storage, can generally be colored any color, is generally lustrous and flexible, and does not generate harmful halogen gas at the time of combustion, as well as flameproof mesh sheet comprising the same.
In accordance with these and other objects, there is provided a flame retardant suitable for use in sheets comprising a polyolefin resin aqueous dispersion having a resin solid content of 25-75 wt %, 40 to 130 parts by weight of an ammonium polyphosphate compound based on 100 parts by weight of said polyolefin resin aqueous dispersion, and 60 to 150 parts by weight of a metal hydroxide based on 100 parts by weight of the solid content of said polyolefin resin aqueous dispersion.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.